Figure 4.

Physiological suppression of Kv1.4/Kv1.5 heteromultimeric channels mediated by the SH3-dependent interaction of Src with the Kv1.5 proline-rich SH3 domain ligand sequence. Currents evoked in Kv subunit cRNA-injected X. laevis oocytes by a 1-s voltage step from a holding potential of −80 mV to a test potential of +80 mV were measured by using a two-electrode voltage clamp both immediately before and 9–12 h after a second injection with either H20, Src_CI, or Src_CISH3_KO cRNA. Current traces depicted were measured after the second injection and were chosen on the basis of exhibiting the closest peak current magnitude to the mean for the represented experimental condition (ND, not determined). Current traces within each column are drawn to the same scale, with the following peak current magnitudes after H20 treatment: Kv1.4, 13.6 μA; Kv1.5, 9.9 μA; Kv1.5-ΔPro, 5.0 μA; Kv1.4-Kv1.5-Tandem, 11.1 μA; Kv1.4-Kv1.5-tandem-ΔPro, 2.1 μA. Bar graphs depict the mean ± SEM peak current ratios for each oocyte recorded after reinjection to that recorded before reinjection, and were analyzed using one-way ANOVA and the Scheffé paired-comparison test. Group sizes were between 12 and 29 oocytes. NS, no significant differences; ***, P < 0.01.